Separator membranes are important components of batteries. These membranes serve to prevent contact of the anode and cathode of the battery while permitting electrolyte to pass there through. Additionally, battery performance attributes such as cycle life and power can be significantly affected by the choice of separator. Safety can also be related to separator attributes, and certain separators are known to reduce occurrence of Li metal plating at the anode and even dendrite formation.
Separator membranes of battery cells are, in some instances, formed from bodies of porous polymer materials. In other instances, separator membranes are formed from bodies of fibrous or particulate material, and such materials can include glass fibers, mineral fibers such as asbestos, ceramics, synthetic polymeric fibers as well as natural polymeric fibers such as cellulose.
There are a number of problems with the presently utilized separator membranes. Such membranes materials are often expensive, and given the fact that a typical battery system will include relatively large volumes of membranes, the cost of the membranes can be a significant component of overall battery costs.
Low cost battery separator membrane materials can be inefficient in preventing dendrite bridging, and hence must be made relatively thick. However, this thickness increases the internal resistance of the battery thereby decreasing its efficiency, and also increases battery size.
Thus, there is a need for a separator configuration that is efficient, low in cost, safe and easy to utilize. Currently, separators for lithium ion cells are expensive—averaging ˜$2.00/m2, which is about 11% of the cost in a high energy cell and ˜23% of the cost of a high power cell. To further reduce the cost of lithium ion batteries, an inexpensive separator needs to be developed.